Work and energy. Test Work

1 option

1. A body weighing 1 kg rises to a height of 5 m. What is the work done by gravity when lifting a body?

A. 50J B.150J C. 250J.

2. Determine the minimum power that the lift engine must have to lift a load weighing 0.05 tons to a height of 10 m in 5 s.

A.2kW B.1kW C.3kW.

3. When riding a bicycle on a horizontal road at a speed of 9 km/h, a power of 30 W is developed. Find driving force.

A.12N B. 24N C. 40N.

4. A body weighing 2 kg has a potential energy of 10 J. To what height above the ground is the body raised if the zero of the potential energy reference is at the surface of the earth?

A.1m B. 0.5m C. 2m.

5. What is the potential energy of the impact part of a pile hammer weighing 300 kg, raised to a height of 1.5 m?

A. 4500J B. 5000J C. 6000J.

6. What maximum potential energy will a bullet fired from a gun have if its speed at exit is 600 m/s and its mass is 9 g?

A. 460J B.1620J C. 2500J.

7. At what speed was a stone thrown vertically upward if it rose to a height of 5m?

A.10m/s B.5m/s C. 2m/s.

8. An airplane weighing 2 tons moves in a horizontal direction at a speed of 50 m/s. Being at an altitude of 420 m, it begins to descend with the engine turned off and reaches the airfield track at a speed of 30 m/s. What is the work done by the air resistance force during a gliding flight?

A. -10MJ B.10MJ C. -20MJ.

9. Two carts are moving towards each other at a speed of 4m/s each. After the collision, the second cart received a speed in the direction of movement of the first cart equal to 6 m/s, and the first one stopped. Calculate the mass of the first cart if the mass of the second is 2 kg.

10. A stone weighing 20 g, released vertically upward from a slingshot, the rubber band of which was stretched by 20 cm, rose to a height of 40 cm. Find the stiffness of the harness.

Option 2

1. A body weighing 2 kg is raised to a height of 2 m. What is the work done by gravity when lifting a body?

A. 40J B. 80J C. 60J.

2. Calculate the power of a pump that supplies 1200 kg of water every minute to a height of 20 m.

A.4kW B.10kW C. 20kW.

3. The thrust force of a supersonic aircraft at a flight speed of 2340 km/h is 220 kN. What is the power of the aircraft engines in this flight mode?

A.143MW B.150MW C. 43MW.

4. A body raised above the ground to a height of 2 m has a potential energy of 40 J. What is the mass of this body if the potential energy zero is at the surface of the earth?

A. 2kg B. 4kg C. 5kg.

5. What is the change in potential energy of a load weighing 200 kg falling to the ground from a height of 2 m?

A. -4500J B. -4000J C. 4000J.

6.What is the kinetic energy of a body weighing 3 kg moving at a speed of 4 m/s?

A. 20J B. 30J C. 24J.

7. A ball is thrown vertically upward at a speed of 10 m/s. Determine the maximum height to which the ball will rise.

A. 10m B. 5m C. 20m.

8. A stone thrown vertically upward with a speed of 20 m/s fell to the ground with a speed of 10 m/s. Stone weight 200g. What is the work done by the air resistance force?

A. -30J B. 30J C. -40J.

9. Two balls are moving towards each other at the same speed. The mass of the first ball is 1 kg. What mass must the second ball have so that after the collision the first ball stops and the second rolls back at the same speed?

10. When preparing a toy pistol for firing, a spring with a stiffness of 800 N/m was compressed by 5 cm. What speed does a bullet of mass 20 g acquire when fired in a horizontal direction?

Option 3

1. A ball of mass m moves with speed v and collides with the same stationary ball. Assuming the impact to be absolutely elastic, determine the velocities of the balls after the collision.

A. v 1 =0; v 2 =v B. v 1 =0; v 2 =0 V. v 1 =v; v 2 =v.

2. What is the modulus of change in momentum of a body of mass m, moving with speed v, if after a collision with the wall the body began to move in the opposite direction with the same speed in modulus?

A. 0 B. mv C. 2mv .

3. A material point with a mass of 1 kg moves uniformly in a circle at a speed of 10 m∕ s. Determine the change in momentum over half the period.

A. 0 kg·m∕s B. 14 kg·m∕s C. 20 kg·m∕s.

4. How many times is the potential energy accumulated by a spring when compressed from the equilibrium position by 2 cm less than when the same spring is compressed by 4 cm?

A. 2 times B. 8 times C. 4 times.

5. How will the kinetic energy of a body change when its speed doubles?

A. Will increase by 4 times B. Will decrease by 4 times C. Will increase by 2 times.

6. A bullet is fired from a spring pistol located at a height of 2 m above the ground. The first time vertically upward, the second time horizontally. In what case will the speed of the bullet approaching the surface of the earth be the greatest? Neglect air resistance. The speed at which a bullet leaves a pistol is assumed to be the same in all cases.

A. In the first B. In the second C. In all cases, the final velocity of the bullet modulo will be the same.

7. The figure shows the trajectory of a body thrown at an angle to the horizon (neglect air resistance). Kinetic energy is equal to potential energy at a point

A. 2 B. 3 C. 4

G. Equal at all points.

8. A proton moving at a speed of 2·10 4 m/s collided with the stationary nucleus of a helium atom. Calculate the speed of the nucleus of a helium atom after the impact if the speed of the proton decreased to 0.8 10 4 m/s. The mass of a helium nucleus is 4 times greater than the mass of a proton.

9. When preparing a toy pistol for firing, a spring with a stiffness of 800 N/m was compressed by 5 cm. What speed does a bullet weighing 20 g acquire when fired in the horizontal direction?

10. Calculate the average soil resistance force if a body weighing 2 kg, thrown vertically down from a height of 250 m with an initial speed of 20 m/s, plunged into the ground to a depth of 1.5 m.

1. When moving in a straight line, the speed material point directed: 1) to the same direction as the movement; 2) against the direction of movement; 4) regardless of the direction of movement;
2. Physical quantity, equal to the ratio of the movement of a material point to the physically short period of time during which this movement occurred, is called1) average speed uneven movement material point; 2) instantaneous speed of a material point; 3) the speed of uniform motion of a material point.
3. In which case is the acceleration module greater? 1) the body moves at a high constant speed; 2) the body quickly gains or loses speed; 3) the body slowly gains or loses speed.
4. Newton’s third law describes: 1) the action of one body on another; 2) the action of one material point on another; 3) interaction of two material points.
5. The locomotive is coupled to the carriage. The force with which the locomotive acts on the car is equal to the forces preventing the movement of the car. Other forces do not affect the movement of the car. Consider the reference frame connected to the Earth to be inertial. In this case: 1) the car can only be at rest; 2) the car can only move at a constant speed; 3) the car is moving at a constant speed or is at rest; 4) the car is moving with acceleration.
6. An apple weighing 0.3 kg falls from a tree. Choose the correct statement: 1) the apple acts on the Earth with a force of 3N, but the Earth does not act on the apple; 2) The Earth acts on the apple with a force of 3N, but the apple does not act on the Earth; 3) the apple and the Earth do not affect each other; 4) the apple and the Earth act on each other with a force of 3 N.
7. When a force of 8N is applied, the body moves with an acceleration of 4m/s2. What is its mass?1) 32 kg; 2) 0.5kg; 3) 2 kg; 4) 20kg.
8. With dry friction, the maximum static friction force is: 1) greater than the sliding friction force; 2) less sliding friction force; 3) equal to the sliding friction force.
9. The elastic force is directed: 1) against the displacement of particles during deformation; 2) in the direction of particle displacement during deformation; 3) nothing can be said about its direction.
10. How does the mass and weight of a body change when it moves from the equator to the Earth’s pole? 1) the mass and weight of the body do not change; 2) body weight does not change, weight increases; 3) body weight does not change, weight decreases; 4) body mass and weight decrease.
11. Spacecraft after turning off the rocket engines, it moves vertically upward, reaches the top point of the trajectory and then moves downward. At what part of the trajectory in the ship is the state of weightlessness observed? Air resistance is negligible.1) only during upward movement; 2) only during downward movement; 3) only at the moment of reaching the top point of the trajectory; 4) during the entire flight with the engines not running.
12. An astronaut on Earth is attracted to it with a force of 700 N. With what approximate force will it be attracted to Mars while on its surface, if the radius of Mars is 2 times, and the mass is 10 times less than that of the Earth? 1) 70 N; 2) 140 N; 3) 210 N; 4) 280N.
Part 2
1) A body is thrown at an angle to the horizontal with an initial speed of 10 m/s. What is the speed of the body at the moment when it is at a height of 3 m? Determine the force of gravity acting on a body of mass 12 kg raised above the Earth at a distance equal to a third of the Earth's radius.
2) How much work must be done to lift a load weighing 30 kg to a height of 10 m with an acceleration of 0.5 m/s2?

This test contains 23 task options different levels on the topic "Work, power, simple mechanisms"for 9th grade (according to the physics textbook for 9th grade by N.M. Shakhmaev, A.V. Bunchuk). Each option contains a different number of qualitative and computational problems of different levels. Knowing individual characteristics student, you can select feasible tasks for each child in this work. I will be glad if this publication is useful to someone. Download, process. Good luck!

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9th grade (according to Shakhmaev).

Test No. 3.

Work, power, simple mechanisms.

Option No. 1

A body of mass 1 kg with a force of 20 N rises to a height of 5 m. What is the work done by this force?
Give a detailed answer: is it possible to move a sailboat by directing a flow of air from a powerful fan located on the boat onto the sails?
Determine the minimum power that the lift motor must have to lift a load weighing 50 kg to a height of 10 m in 5 s. Find efficiency
How much work is done by the force of gravity acting on a raindrop weighing 20 g when it falls from a height of 1 km?

Option No. 2

A body weighing 1 kg rises to a height of 5 m. What is the work done by gravity?
Give a detailed answer: a stone and a tennis ball are hit with a stick. Why does the ball, all other things being equal, fly further than the stone?
Calculate the power of a pump that supplies 1200 kg of water every minute to a height of 20 m.
A stone with a mass of 400 g is thrown vertically upward at a speed of 20 m/s. What are the kinetic and potential energies of the stone at a height of 15 m?
A piano weighing 300 kg was moved through a sixth floor window located 16 m above the sidewalk using a lifting device in 50 s. Determine work, power, efficiency.

Option #3

A weightlifter, lifting a barbell, does 5 kJ of work in 2 s. Determine the power and efficiency.
What mass of load can a lifting machine lift to a height of 30 m in 4 minutes if the engine power is 5 kW?

Option No. 4

Cat Matroskin and Sharik towed Uncle Fyodor's car to Prostokvashino for 1 hour, acting with a force of 120 N. The distance to Prostokvashino is 1 km. Determine the work, efficiency. and power
What is the power developed by the tractor at a speed of 9.65 km/h and a traction force of 15 kN?
How much work is done by uniformly lifting an iron beam with a volume of 0.1 m 3 to a height of 15 m?

Option #5

1. A boy weighing 40 kg climbed in 30 s to the second floor of a house located at a height of 8 m. Determine the work and power
What work does an excavator do when lifting soil with a volume of 14 m with a bucket? 3 to a height of 5 m? Soil density 1400 kg/m 3 .
The climber climbed the mountains to a height of 2 km. Determine the mechanical work performed by the climber when climbing if his mass together with equipment is 85 kg.
What mass of load can a lifting machine lift to a height of 30 m in 4 minutes if the engine power is 5 kW? Find efficiency
A force of 4 N and 20 N acts at the ends of the lever. The length of the lever is 1.5 m. Where is the fulcrum if the lever is in equilibrium?

Option number 6.

When walking, a person takes 10,000 steps for 2 hours (40 J of work is done per step). Determine work, power and efficiency.
How much work is done by the force of gravity acting on a raindrop weighing 20 g when it falls from a height of 2 km?
The thrust force of a supersonic aircraft at a flight speed of 2340 km/h is 220 kN. Find the power of the aircraft's engines in this flight mode.
Weights of masses 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the length of the lever if the lever is in equilibrium.

Option No. 7

Baba Yaga's stupa (mass 70 kg) flies 120 km in 1 hour. Determine the work, power
A crane lifted a load weighing 5 tons to a height of 10 m in 45 s. Determine the crane motor power and efficiency
A diesel locomotive at a speed of 54 km/h develops a traction force of 400 kN. How much work is done to move the train for 1 minute?
A force of 4 N and 20 N acts at the ends of the lever. The length of the lever is 1.5 m. Where is the fulcrum if the lever is in equilibrium?

Option No. 8

Carlson lifts a Kid weighing 30 kg onto the roof of a house 20 m high in 10 s. Determine the work and power of Carlson
The spring of a toy gun, compressed by 3 cm, pushes the ball out in 1 s, acting on it with a force of 10 N. Determine work, power and efficiency.
The Zhiguli car travels 100 m in 6.25 s, developing a thrust of 3 kN. Determine work and power
4.Nuclear icebreaker, developing a power of 32400 kW, covered 20 km in ice in 5 hours. Determine the average resistance force to the movement of the icebreaker.
Weights of masses 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the length of the lever if the lever is in equilibrium.

Option number 9.

A crane lifts a concrete slab weighing 5 tons to a height of 9 m in 1 minute. Determine work, power and efficiency.
The boy evenly lifted a bucket of water from a well once in 20 s, and the other in 30 s. Was the same work done in these cases? What can you say about the power when performing these jobs?
A cyclist does 800 J of work in 10 s. What is the cyclist’s power?
What mass of load can a lifting machine lift to a height of 30 m in 4 minutes if the engine power is 5 kW?
A force of 4 N and 20 N acts at the ends of the lever. The length of the lever is 1.5 m. Where is the fulcrum if the lever is in equilibrium?

Option No. 10

How long will it take to pump out water weighing 2 tons if the pump power is 1.5 kW? The height of water rise is 20 m. Find the efficiency.
Academician B. S. Jacobi invented the electric motor in 1834. In the first version, the electric motor lifted a load weighing 5 kg to a height of 60 cm in 2 s. Determine the engine power.
What is the power developed by the tractor at a speed of 9 km/h and a traction force of 10 kN?
The nuclear icebreaker, developing a power of 32400 kW, covered 20 km in ice in 5 hours. Determine the average resistance force to the movement of the icebreaker.
Weights of masses 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the length of the lever if the lever is in equilibrium.

Option No. 11

.To what height must a weight of 100 N be raised to do work?

200 J?

Determine the work done when lifting a load weighing 4 N to a height of 4 m
Determine the work done by a 400 W motor in 30 s. What is the efficiency?
What mass of load can a lifting machine lift to a height of 30 m in 4 minutes if the engine power is 5 kW?
A force of 4 N and 20 N acts at the ends of the lever. The length of the lever is 1.5 m. Where is the fulcrum if the lever is in equilibrium?

Option No. 12

How long must a 200 W electric motor run to do 2500 J of work?
When riding a bicycle on a horizontal road at a speed of 9 km/h, a power of 30 W is developed. Find the driving force.
Calculate the power of a pump that supplies 1200 kg of water every minute to a height of 20 m

The nuclear icebreaker, developing a power of 32,400 kW, covered 20 km in ice in 5 hours.
Determine the average resistance force to the movement of the icebreaker and efficiency. icebreaker
Weights of masses 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the length of the lever if the lever is in

balance.

Option No. 13

A crane lifts a load at a constant speed of 5.0 m/s. Crane power 1.5 kW. Which

can this crane lift the load?

When preparing a toy gun for firing, a spring with a stiffness of 800 N/m

compressed by 5 cm. What speed will a 20 g bullet acquire when fired in a horizontal direction?

A force of 4 N and 20 N acts at the ends of the lever. The length of the lever is 1.5 m. Where is the fulcrum if the lever is in equilibrium?

Option No. 14

A ball with a mass of 100 g fell freely onto a horizontal platform, having a speed of 10 m/s at the moment of impact. Find the height of the fall, neglecting friction.
From a dam 20 m high falls 1.8∙10 4 t of water. What kind of work is done?
Determine the potential energy of a spring with a stiffness of 1.0 kN/m if it is known that the spring compression is 30 mm.
Carlson lifts a Kid weighing 20 kg onto the roof of a house 20 m high in 10 s. Determine the work and power of Carlson

Option No. 15

Determine the net power of a motorcycle engine if, at a speed of 108 km/h, its traction force is 350 N.
What work is done when lifting from the ground the materials needed to build a column 20 m high with a cross-sectional area of 1.2 m 2 ? The density of the material is 2.6∙10 3 kg/m3.
Determine at what speed a ball must be thrown down from a height of 3 m so that it bounces to a height of 8 m.
A force of 4 N and 20 N acts on the ends of the lever. The length of the lever is 2 m. Where is the fulcrum if the lever is in equilibrium?

Option No. 16

At an aircraft speed of 900 km/h, its four engines develop a net power of 30 MW. Find the thrust of each engine in this flight mode.
Determine the work that must be done when digging a well with a diameter of 1.0 m and a depth of 10 m, if the density of the soil is 1.8∙10 3 kg/m 3 . Consider that the soil is scattered in a thin layer over the surface of the earth.

3. A stone weighing 20 g, released vertically upward from a slingshot, a rubber band which was stretched by 10 cm, rose to a height of 40 cm. Find the stiffness of the spring.

4. Determine the minimum power that the lift motor must have to lift a load weighing 50 kg to a height of 10 m in 5 s. Find efficiency

Option No. 17

A crane lifts a load weighing 500 kg uniformly to a height of 10 m in 50 s. Determine the efficiency of the crane if its motor power is 1.5 kW.
The spring, compressed by 30 cm, fully straightens. How much work is done by the elastic force if the spring stiffness is 100 N/m?
Determine the work done by the friction force if a body weighing 2 kg changes its speed from 4 to 3 m/s?
A ball of mass 250 g is thrown vertically upward at a speed of 20 m/s. What is its kinetic energy at a height of 10 m?

Option No. 18

The box is pulled evenly along a horizontal surface by a rope forming an angle of 60° with the horizon. The force applied to the rope is 25N. How much work is done when moving a box at a distance of 4 m?
At a height of 15m above the Earth's surface building block has a potential energy of 1500 kJ. What is its mass?
The spring has a stiffness of 2500 N/m. What energy does the spring have if it is compressed by 10 cm?
An arrow with a mass of 20 g is fired vertically upward from a bow at a speed of 20 m/s. Determine its kinetic energy at a height of 15 m.
The nuclear icebreaker, developing a power of 32400 kW, covered 20 km in ice in 5 hours. Determine the average resistance force to the movement of the icebreaker and efficiency. icebreaker

Option No. 19

A body of mass 1 kg with a force of 20 N rises to a height of 5 m. What is the work done by this force?
A ball placed under water to a depth of 30 cm is pushed out with a force of 5 N. Define the job.
The spring was compressed by 4 cm. The spring stiffness is 100 kN/m. What work will it do?
The useful work is 20kN, the total energy expended is 40000 N. Find the efficiency.
Name the energy transitions during a fall

Option No. 20

Weights of masses 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the distance to the second load if the lever is in equilibrium.
The spring was compressed by 50 cm. The spring stiffness was 10 kN/m. What is the energy of the spring?
Determine the work done by gravity when a body weighing 4 kg falls from a height of 200 cm.
What is meant by body energy? List the types of energy.

Option No. 21

The climber climbed the mountains to a height of 1.5 km. Determine the mechanical work performed by the climber when climbing if his mass together with equipment is 100 kg.
What is the gain of the moving block?
Write formulas various types energies
Where and for what purpose is the gate used?

Option No. 22

2. What is the purpose of an inclined plane?

3. The spring, compressed by 10 cm, fully straightens. How much work is done by the elastic force if the spring stiffness is 1 kN/m?

4. At a height of 10 m above the Earth's surface, a building block has a potential energy of 150 kJ. What is its mass?

Option No. 23

1. What is the gain of the moving block?

2. A nuclear icebreaker, developing a power of 32400 kW, covered 20 km in ice in 5 hours. Determine the average resistance force to the movement of the icebreaker.

3. Weights of masses 4 and 24 kg are suspended from the lever. The distance from the fulcrum to the larger load is 4 cm. Determine the length of the lever if the lever is in equilibrium.

4. Carlson lifts a Kid weighing 30 kg onto the roof of a house 20 m high in 10 s. Determine the work and power of Carlson

Option No. 24

A crane lifts a load at a constant speed of 5.0 m/s. Crane power 1.5 kW. What kind of load can this crane lift?
Determine at what height the kinetic energy of a ball thrown vertically upward at a speed of 23 m/s is equal to its potential?
When preparing a toy pistol for firing, a spring with a stiffness of 800 N/m was compressed by 5 cm. What speed will a 20 g bullet acquire when fired in a horizontal direction?
Forces of 5 and 6 N act on the lever from below at angles of 45 and 30 degrees at a distance of 20 and 40 cm, respectively, from the support located in the middle of the lever. Find the force that can be used to balance the system by applying it vertically at a distance of 10 cm from the axis of rotation.